The effect of temperature on permittivity measurements of aqueous solutions of glucose for the development of non-invasive glucose sensors based on electromagnetic waves

This article presents for the first time an empirical study that shows the importance of considering temperature when analyzing the permittivity (dielectric constant) of aqueous glucose solutions of various concentrations. The permittivity is a parameter that is investigated by researchers as a biomarker for non-invasive measurement of glucose without drawing blood. The development of this technology will allow personalized healthcare diagnostics to monitor and prevent diabetes. Since human glucose levels in the blood vary in the range of a few milligrams per decilitre, estimating such small variations of glucose will require a highly accurate and repeatable sensing technology. Electromagnetic (EM) waves, specifically in the microwave and terahertz frequency ranges, have shown promise in detecting changes in the electrical properties of blood plasma as they relate to glucose concentration. However, it’s important to note that while this technology shows promise, it is still in the research and development phase. It is shown here that the body temperature can affect the accuracy of the blood glucose measurements. Experiments were conducted with different glucose concentration solutions under various temperatures and the complex permittivity of the glucose was studied across a wide frequency range from 400 MHz to 11 GHz. The rise in thermal energy normally causes dipolar liquids like water to vibrate and rotate disrupting the alignment of the dipoles in response to an electric field thereby reducing its permittivity. Empirical results however show that for aqueous solution of glucose the permittivity increases with rise in temperature from 16◦C to 37◦C. This is attributed to the polar nature of the water and glucose molecules that becomes more pronounced with increased thermal energy. Based on the experimental results an accurate analytical expression is derived that considers the temperature of the aqueous glucose solution. The accuracy of the analytical expression is shown experimentally to be above 99%. The findings from the study should enable the design of accurate noninvasive glucose monitoring devices based on electromagnetic sensing techniques

Design of a Planar Sensor Based on Split-Ring Resonator for Non-invasive Permittivity Measurement

The permi)ivity of a material is an important parameter to characterize the degree of polarization of a material and identify components and impurities. This paper presents a non-invasive measurement technique to characterize materials in terms of their permi)ivity based on a modified metamaterial unit-cell sensor. The sensor consists of a complementary split-ring resonator (C-SRR), but its fringe electric field is contained with a conductive shield to intensify the normal component of the electric field. It is shown that by tightly electromagnetically coupling opposite sides of the unit-cell sensor to the input/output microstrip feedlines, two distinct resonant modes are excited. Perturbation of the fundamental mode is exploited here for determining the permi)ivity of materials. The sensitivity of the modified metamaterial unit-cell sensor is enhanced four-fold by using it to construct a tri-composite split-ring resonator (TC-SRR). The measured results confirm that the proposed technique provides an accurate and inexpensive solution to determine the permi)ivity of materials

Frequency-Selective Surface-Based MIMO Antenna Array for 5G Millimeter-Wave Applications

In this paper, a radiating element consisting of a modified circular patch is proposed for MIMO arrays for 5G millimeter-wave applications. The radiating elements in the proposed 2 × 2 MIMO antenna array are orthogonally configured relative to each other to mitigate mutual coupling that would otherwise degrade the performance of the MIMO system. The MIMO array was fabricated on Rogers RT/Duroid high-frequency substrate with a dielectric constant of 2.2, a thickness of 0.8 mm, and a loss tangent of 0.0009. The individual antenna in the array has a measured impedance bandwidth of 1.6 GHz from 27.25 to 28.85 GHz for S11 ≤ −10 dB, and the MIMO array has a gain of 7.2 dBi at 28 GHz with inter radiator isolation greater than 26 dB. The gain of the MIMO array was increased by introducing frequency-selective surface (FSS) consisting of 7 × 7 array of unit cells comprising rectangular C-shaped resonators, with one embedded inside the other with a central crisscross slotted patch. With the FSS, the gain of the MIMO array increased to 8.6 dBi at 28 GHz. The radiation from the array is directional and perpendicular to the plain of the MIMO array. Owing to the low coupling between the radiating elements in the MIMO array, its Envelope Correlation Coefficient (ECC) is less than 0.002, and its diversity gain (DG) is better than 9.99 dB in the 5G operating band centered at 28 GHz between 26.5 GHz and 29.5 GHz

Frequency-selective surface-based MIMO antenna array for 5G millimeter-wave applications

In this paper, a radiating element consisting of a modified circular patch is proposed for MIMO arrays for 5G millimeter-wave applications. The radiating elements in the proposed 2 x 2 MIMO antenna array are orthogonally configured relative to each other to mitigate mutual oupling that would otherwise degrade the performance of the MIMO system. The MIMO array was fabricated on Rogers RT/Duroid high-frequency substrate with a dielectric constant of 2.2, a thickness of 0.8 mm, and a loss tangent of 0.0009. The individual antenna in the array has a measured impedance bandwidth of 1.6 GHz from 27.25 to 28.85 GHz for S11 less than or equal to -10 dB, and the MIMO array has a gain of 7.2 dBi at 28 GHz with inter radiator isolation greater than 26 dB. The gain of the MIMO array was increased by introducing frequency-selective surface (FSS) consisting of 7 x 7 array of unit cells comprising rectangular C-shaped resonators, with one embedded inside the other with a central crisscross slotted patch. With the FSS, the gain of the MIMO array increased to 8.6 dBi at 28 GHz. The radiation from the array is directional and perpendicular to the plain of the MIMO array. Owing to the low coupling between the radiating elements in the MIMO array, its Envelope Correlation Coefficient (ECC) is less than 0.002, and its diversity gain (DG) is better than 9.99 dB in the 5G operating band centered at 28 GHz between 26.5 GHz and 29.5 GHz

Design of a planar sensor based on split-ring resonators for non-invasive permittivity measurement

The permittivity of a material is an important parameter to characterize the degree of polarization of a material and identify components and impurities. This paper presents a non-invasive measurement technique to characterize materials in terms of their permittivity based on a modified metamaterial unit-cell sensor. The sensor consists of a complementary split-ring resonator (C-SRR), but its fringe electric field is contained with a conductive shield to intensify the normal component of the electric field. It is shown that by tightly electromagnetically coupling opposite sides of the unit-cell sensor to the input/output microstrip feedlines, two distinct resonant modes are excited. Perturbation of the fundamental mode is exploited here for determining the permittivity of materials. The sensitivity of the modified metamaterial unit-cell sensor is enhanced four-fold by using it to construct a tri-composite split-ring resonator (TC-SRR). The measured results confirm that the proposed technique provides an accurate and inexpensive solution to determine the permittivity of materials

Oculocutaneous anthrax: detection and treatment

Sarada David1, Jayanthi Peter1, Renu Raju2, P Padmaja2, Promila Mohanraj21Department of Ophthalmology, Schell Eye Hospital, Christian Medical College Hospital, Vellore, India; 2Department of Microbiology, Christian Medical College Hospital, Vellore, IndiaAbstract: Anthrax, a zoonotic disease that primarily affects herbivores, has received recent attention as a potential agent of bioterrorism. We report a patient who presented with a 4-day history of pain, watering and difficulty in opening the left upper and lower eyelids, and fever. Clinical examination revealed brawny nonpitting edema with serosanguinous discharge. The history of the death of his sheep 1 week prior to the illness provided the clue to the diagnosis. Although standard cultures of the blood and the serous fluid from the lesion were negative, probably as a result of prior treatment, the diagnosis of cutaneous anthrax was made by a polymerase chain reaction (PCR) test of the serous fluid. Serial photographs demonstrating resolution of the lesion with appropriate antibiotic therapy are presented.Keywords: anthrax, polymerase chain reaction, treatmen

Effect of metabolite and temperature on artificial human sweat characteristics over a very wide frequency range (400 MHz–10.4 GHz) for wireless hydration diagnostic sensors

Sweat is an important biofluid that is excreted by the human body. It contains physiological biomarkers that provide vital information on the general health condition of the body. As a result, analysis of electrolytes in this biofluid is gaining traction in the development of non-invasive sweat diagnostics to determine level of dehydration, cystic fibrosis and illicit drugs. This paper presents a wireless measurement modality of permittivity properties of sweat of different metabolite concentration levels exemplifying the full spectrum of human sweat. The artificial sweat used in the study is an analogue of actual human sweat. It is synthesized from a composite mixture of metabolites and minerals including sodium chloride, potassium chloride, Urea and lactic acid. The effect of ambient temperature on the permittivity measurements of the various sweat solutions are studied across a frequency range of 400 MHz to 10.4 GHz. This information is important in the development of wireless radio frequency (RF) non-invasive biosensors

Effect of metabolite and temperature on artificial human sweat characteristics over a very wide frequency range (400 MHz–10.4 GHz) for wireless hydration diagnostic sensors

Sweat is an important biofluid that is excreted by the human body. It contains physiological biomarkers that provide vital information on the general health condition of the body. As a result, analysis of electrolytes in this biofluid is gaining traction in the development of non-invasive sweat diagnostics to determine level of dehydration, cystic fibrosis and illicit drugs. This paper presents a wireless measurement modality of permittivity properties of sweat of different metabolite concentration levels exemplifying the full spectrum of human sweat. The artificial sweat used in the study is an analogue of actual human sweat. It is synthesized from a composite mixture of metabolites and minerals including sodium chloride, potassium chloride, Urea and lactic acid. The effect of ambient temperature on the permittivity measurements of the various sweat solutions are studied across a frequency range of 400 MHz to 10.4 GHz. This information is important in the development of wireless radio frequency (RF) non-invasive biosensors

The effect of temperature on permittivity measurements of aqueous solutions of glucose for the development of non-invasive glucose sensors based on electromagnetic waves

This article presents for the first time an empirical study that shows the importance of considering temperature when analyzing the permittivity (dielectric constant) of aqueous glucose solutions of various concentrations. The permittivity is a parameter that is investigated by researchers as a biomarker for non-invasive measurement of glucose without drawing blood. The development of this technology will allow personalized healthcare diagnostics to monitor and prevent diabetes. Since human glucose levels in the blood vary in the range of a few milligrams per decilitre, estimating such small variations of glucose will require a highly accurate and repeatable sensing technology. Electromagnetic (EM) waves, specifically in the microwave and terahertz frequency ranges, have shown promise in detecting changes in the electrical properties of blood plasma as they relate to glucose concentration. However, it's important to note that while this technology shows promise, it is still in the research and development phase. It is shown here that the body temperature can affect the accuracy of the blood glucose measurements. Experiments were conducted with different glucose concentration solutions under various temperatures and the complex permittivity of the glucose was studied across a wide frequency range from 400 MHz to 11 GHz. The rise in thermal energy normally causes dipolar liquids like water to vibrate and rotate disrupting the alignment of the dipoles in response to an electric field thereby reducing its permittivity. Empirical results however show that for aqueous solution of glucose the permittivity increases with rise in temperature from 16 °C to 37 °C. This is attributed to the polar nature of the water and glucose molecules that becomes more pronounced with increased thermal energy. Based on the experimental results an accurate analytical expression is derived that considers the temperature of the aqueous glucose solution. The accuracy of the analytical expression is shown experimentally to be above 99%. The findings from the study should enable the design of accurate non-invasive glucose monitoring devices based on electromagnetic sensing techniques